The long range goal of the proposed research is to provide a thorough understanding of the complex regulation of gonadotropin and prolactin secretion by the adenohypophysis. Particular emphasis is placed on studies designed to elucidate the chemical nature and physiological significance of the hypothalamic gonadotropin releasing factors. Specifically, further attempts to isolate an LRF distinct from the decapeptide LRF and to separate FSH-releasing from LH-releasing activity will be made. Studies on the mechanism of release of these releasing factors from the hypothalamus and their mechanism of action at the pituitary cellular level will be continued. Attempts will be made to further clarify the role of monoamines, other possible synaptic transmitters, cyclic nucleotides, and prostaglandins on gonadotropin and prolactin secretion. Factors influencing the responsiveness of the pituitary to LRF will be systematically explored. The ontogeny of gonadotropin and prolactin secretion will be evaluated in the rat, and a number of additional studies designed to elucidate further the pathways involved in the control of gonadotropin secretion are planned.